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Abstract:

An annular seal for a setting tool in a packer tieback extension
comprises a downhole oriented packer cup assembly. As the tool is run in
the hole the packer cup flexes as the rising hydrostatic pressure
equalizes across the cup into what started as a zone with atmospheric
pressure inside the packer tieback extension. Once the pressure is
equalized the self energizing feature of the packer cup maintains grit
and debris in the mud from entering the tieback extension where the
spring loaded dogs of the setting tool are held in a retracted position.
If the seal fails to equalize and allows a large differential across the
setting sleeve from the surrounding annulus, the rupture disc breaks
inwardly into the tieback extension so that pressure is equalized. If the
packer is never set after being lowered to depth and the pressure from
the tieback extension is equalized into the annulus.

Claims:

1. An apparatus for protecting from debris a component of a running tool
disposed within a subterranean tool being run for deployment at a
subterranean location, comprising: a running tool mandrel disposed
adjacent a component of a subterranean tool to define an annular gap
therebetween defining an annular space where components need to be
protected from subterranean debris; a seal assembly spanning said annular
gap; said annular space, which is closed to flow toward the subterranean
location surrounding said mandrel by said seal assembly, is selectively
communicated through at least one mandrel wall opening that is
selectively opened by defeat of a pressure sensitive barrier in said
opening, said pressure sensitive barrier responding to differential
pressure between pressure at said annular space and the subterranean
location surrounding said mandrel.

2. The apparatus of claim 1, wherein: said barrier responds to pressure
differentials in opposed directions.

3. The apparatus of claim 2, wherein: said barrier comprises at least one
rupture disc.

4. The apparatus of claim 2, wherein: said seal assembly allowing flow
into said annular space as the subterranean tool is run in to equalize
initially lower pressure in said annular space with increasing
surrounding hydrostatic pressure to reduce differential pressure on the
component of the subterranean tool.

5. The apparatus of claim 4, wherein: said seal assembly closes said gap
upon equalizing surrounding hydrostatic pressure into said annular space.

6. The apparatus of claim 4, wherein: said seal assembly prevents flow
out of said annular space.

7. The apparatus of claim 4, wherein: said seal assembly shape comprises
a bias to retain said annular gap closed.

8. The apparatus of claim 4, wherein: said seal assembly is supported by
said running tool mandrel.

9. The apparatus of claim 8, wherein: said seal assembly comprises at
least one cup seal.

10. The apparatus of claim 9, wherein: said cup seal has an open end
facing into said annular space.

11. The apparatus of claim 10, wherein: said at least one cup seal
comprises a plurality of cup seals.

12. The apparatus of claim 11, wherein: said cup seals have the same open
end facing orientation.

13. The apparatus of claim 9, wherein: said running tool mandrel further
comprises a continuous ring mounted to said mandrel and disposed in close
proximity to said annular gap to limit the debris able to enter said
annular gap.

14. The apparatus of claim 13, wherein: said mandrel is formed from
multiple components to facilitate mounting said continuous ring to said
mandrel.

Description:

FIELD OF THE INVENTION

[0001] The field of the invention is packers for subterranean use and more
particularly mechanically set packers that need debris exclusion from a
tieback extension or polished bore receptacle while having a backup for
avoiding collapse of the setting sleeve when pressure fails to equalize
for run in and to vent trapped pressure when pulling out of the hole.

BACKGROUND OF THE INVENTION

[0002] In certain applications packers such as line top packers may need
to be in a wellbore for days while being repositioned to accommodate
other procedures. During this time the running tool that will ultimately
set the packer is used to reposition the packer and the liner associated
with the packer. When the time comes to set such a packer the running
tool is released from the assembly, then picked up relative to the packer
to allow spring loaded dogs to extend above the packer tieback extension
so that a subsequent setting down weight will push the tieback extension
to set the packer. The problem in some environments where the wellbore
fluid has fine grit or solid particles is that in the course of the time
that the packer is manipulated in the well before it is set the fine
debris in the drilling mud can migrate into the setting sleeve and foul
the spring-loaded dog mechanism to the point that the dogs will not
extend when pulled free of the tieback extension and subsequent setting
down weight will not set the packer because such force will not be
transmitted to the tieback extension. If the debris accumulation is
severe enough within this annulus, it can also cause difficulty even
achieving this upward movement of the setting tool, and prevent release
of the workstring (drill pipe or tubing) from the liner assembly.

[0003] Prior designs have recognized the need to exclude debris from the
setting sleeve to avoid fouling the spring loaded dog mechanism and have
approached the problem with two split segments that are attached to each
other and span over a part of the annular gap between the setting tool
mandrel and the tieback extension of the packer. This solution has not
been optimal because where the grit in the mud is rather fine there was
still solids migration beyond the barrier and the setting dogs jammed in
the retracted position when pulled out of the tieback extension rather
than springing out so that on setting down they could bear on the top of
the tieback extension for setting the packer.

[0004] U.S. Pat. No. 7,604,048 developed a folding debris barrier 30 that
was set after the packer set by the application of a further set down
weight. It remained retracted with the packer unset and is thus not a
workable solution to a situation of long term grit exposure in an unset
condition as is envisioned for the debris barrier needs for the present
packer application.

[0005] Another solution for sealing a mandrel in a seal bore is offered in
US Publication 20110168387 is to use a foam material that fully spans an
annular gap and is reported to enable pressure equalization through the
open structure of the foam. The potential problem with this design is
that it may plug with particulates internally and will fail to equalize
pressure. The material can also have temperature and mechanical strength
issues that could preclude using it for packer setting sleeve purposes in
harsh grit-laden environments.

[0006] Packer cups have been used as debris barriers and have been
oriented uphole to accumulate debris within the cup. Such orientation
prevents pressure equalization from above to below the uphole oriented
packer cup. Some examples of such a design are: US Publication
2003/0089505; WO2010/097616; U.S. Pat. Nos. 7,604,050; 7,540,323 and
7,011,157. Some designs allow for pressure equalization through debris
catching packer cups by putting holes or ports in them or exposing
mandrel ports near such packer cups, such as U.S. Pat. Nos. 7,882,903;
6,186,227; US Publication 2008/0314600 or US Publication 2007/0062690.

[0007] Combination pressure and vacuum devices have been used for large
storage tanks that are responsive to relieve internal pressure and vacuum
in the storage tank as it is filled or emptied. Such designs are shown in
FIG. 4 in U.S. Pat. No. 6,019,126 but are too large and unwieldy for
subterranean use and are not built to withstand the pressures normally
seen in subterranean wellbores.

[0008] What is needed and provided by the present invention is a debris
barrier that has the capability of pressure equalization as the tool is
delivered so that a zone that starts at atmospheric pressure when run
into the wellbore can equalize with well hydrostatic as such hydrostatic
pressure increases with additional depth for the tool. The same barrier
that allows such pressure equalization also has the capability of
excluding even fine grit by its self energizing configuration after
pressure equalization has occurred. If there is a failure of the
equalization feature a dual acting rupture disc is provided. In one
direction it can prevent collapse of the downhole tool due to large
pressure differentials by letting the hydrostatic pressure rupture the
disc inwardly to relieve the high differential pressure before the
setting sleeve collapses. In some instances the packer has to be removed
without being set and while it is still attached to the running tool.
This can create a volume of trapped high pressure that can injure surface
personnel if that pressure is not relieved before component disassembly.
The dual acting rupture disc responds to a growing differential from
within the tool to the surrounding annulus as the tool is removed from
the wellbore. At some depth the differential as between inside the tool
and the surrounding annulus is high enough to burst the disc in the
outward direction toward the annulus. That way when the packer comes out
of the hole there is no trapped pressure inside. These and other aspects
of the present invention will become more readily understandable from a
review of the detailed description and the associated figures while
understanding that the full scope of the invention is to be found in the
appended claims.

SUMMARY OF THE INVENTION

[0009] An annular seal for a setting tool in a packer tieback extension
comprises a downhole oriented packer cup assembly. As the tool is run in
the hole the packer cup flexes as the rising hydrostatic pressure
equalizes across the cup into what started as a zone with atmospheric
pressure inside the packer setting sleeve. Once the pressure is equalized
the self energizing feature of the packer cup maintains grit and debris
in the mud from entering the setting sleeve where the spring loaded dogs
of the setting tool are held in a retracted position. If the seal fails
to equalize and allows a large differential across the setting sleeve
from the surrounding annulus then the dual acting rupture disc breaks
inwardly into the setting sleeve so that pressure is equalized. If the
packer is never set after being lowered to depth and the pressure from
the setting sleeve has to be equalized into the annulus or else there is
a chance that such trapped pressure will remain if the tool is later
disassembled at the surface. The dual acting rupture disc breaks
outwardly as the unset packer with the running tool are removed together.
Any trapped pressure is thus relieved as the packer is removed so that
surface personnel will not be injured when disassembling the packer and
setting tool combination.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 shows a section view of the setting tool in the setting
sleeve before the packer is set further showing the seal and the rupture
disc placement;

[0011] FIG. 2 is a view of a multi-component hub for the seal of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0012] FIG. 1 illustrates a tieback extension 10 that is part of a known
packer design that can be attached to a liner top. Other applications are
intended but the preferred embodiment seeks to keep debris from entering
the extension 10 as well as protecting the extension 10 against inward
collapse due to an unusual differential pressure situation arising as
will be explained below. Removal of the extension 10 with the associated
packer that is not shown also allows trapped pressure in extension 10 to
equalize with annulus pressure so that personnel will not be injured by
trapped high pressure when disassembling the setting tool from the
extension 10 in the event the packer is not deployed and is retrieved
with the setting tool, as will also be explained below.

[0013] Mandrel 12 is part of the setting tool and is connected to the
packer setting dog sub which encompasses the spring loaded dogs that
reside in extension 10 in a retracted condition. The packer is set in the
known way by raising the dogs out of extension 10 to allow them to spring
out and then setting down the dogs on the top 14 of the extension 10 with
that motion then setting the packer. If fines, grit or debris accumulates
in annular volume 16 where the retracted spring-loaded dogs reside and
get into the mechanisms then there is a chance that the dogs will not
extend when pulled out of the sleeve 10 and setting the packer will not
be possible. It may also become impossible to even release the setting
tool from the liner if the accumulation is severe enough. To keep annular
volume 16 relatively debris free a seal assembly 18 is provided and
mounted to outer mandrel 20 between shoulder 22 and end ring 24 that is
attached to mandrel 20 at thread 26 with the connection secured against
being unthreaded by a pin or pins 28. The seal assembly 18 preferably
comprises multiple packer cups 30 and 32 arranged to have their
respective ends facing downhole, which means in a direction away from a
surface location. Although two cups are shown one or more than two can be
used with open ends 34 and 36 looking downhole.

[0014] Initially on assembly at the surface the annular volume 16 will
have atmospheric pressure trapped therein and filled with a fluid or gel
substance to prevent initial debris accumulation if the extension were
allowed to fill with wellbore fluids on its own. As the packer with the
tieback extension 10 is lowered into a wellbore the wellbore hydrostatic
pressure will increase with depth in the surrounding annulus assuming
there is a liquid level in the annulus. After inserting the assembly of
FIG. 1 into a well for a short distance the annulus pressure greatly
exceeds the trapped atmospheric pressure in annular space 16 and minimal
annulus fluid flow occurs into space 16 across the cups 30 and 32 until
the pressures equalize and the cups 30 and 32 go back out against wall 40
of extension 10. The cups have a shape that biases them outwardly against
wall 40 unless flow induced by pressure differential between annulus 38
and space 16 flexes the cups away from wall 40 as the flow continues.
While some particles may get past the cups 30 and 32 when they are flexed
away from wall 40, that amount is so minimal because the equalization of
pressure happens so fast as the packer is run into the hole that the
working of the spring loaded dogs that reside in the sleeve 10 is not
adversely affected.

[0015] Once the pressure between the annulus 38 and the annular space 16
has equalized, the cups 32 and 30 are strong enough in their contact with
wall 40 to keep solids or other debris from getting past into space 16.
The solids 42 will merely pile up above seal 30 as shown in FIG. 1. The
solids 42 will be smaller than gap 44 created by ring 46 and the top 14
of the setting sleeve 10. In prior designs two segments were brought
together to create a gap such as 44 but in applications of very fine grit
too many solids got into the gap 44. One improvement in the design shown
in FIG. 1 is to use a solid ring 46 and in order to be able to mount ring
46 on the outer mandrel 20 the outer mandrel is made in pieces that are
assembled after the ring 46 is in position. With the ring 46 in the
position of FIG. 1 the component 48 is secured to the outer mandrel 20 at
thread 50 and that connection is held together with ring 52. If this
assembly were a single piece then the ring 46 would need to be in pieces
as in the past. With the components of the outer mandrel 20, 48 as
described above, the ring 46 can be slipped over an end of 20 before the
other component 48 is secured to 20.

[0016] If for any reason there is no pressure equalization past seals 30
and 32 as the packer is run into the hole then trapped atmospheric
pressure can remain in space 16 as the hydrostatic pressure in annulus 38
near the sleeve 10 increases. In very deep wells or wells with high
density wellbore fluids the differential pressure between the annulus 38
hydrostatic and atmospheric pressure inside space 16 can cause sleeve 10
to inwardly collapse. If this happens the setting tool will not be able
to set the packer and separating the setting tool outer mandrel 20 from
the sleeve 10 in a nondestructive way may also become a problem. This
collapse situation is avoided by providing one or more dual action
rupture discs 54 in respective ports 56. To prevent collapse of sleeve 10
inwardly the discs 54 will break inwardly in the direction of arrow 60 to
let pressure in the annulus 38 get into space 16 so that pressure is
equalized with respect to the inside and the outside of extension 10.

[0017] On the other hand there could be occasions where the packer is run
in and never set so that the mandrel 20 comes out of extension 10 for the
setting as described above and then the running/setting tool with its
mandrel 20 are pulled out. In the event that the extension 10 and the
mandrel 20 come out of the hole together, there is a high possibility
that hydrostatic pressure is trapped in annular space 16 because the
seals 30 and 32 are designed to let hydrostatic pressure into space 16 to
avoid collapse of extension 10 on run in but the downhole orientation of
the cup seals 30 and 32 prevents fluid from traveling out of space 16
once past the seals 30 and 32. For those occasions the dual acting
rupture disc 54 will break in the direction of arrow 58 as the mandrel 20
is raised in the wellbore still attached to extension 10. Doing this
assures that there is no trapped pressure in space 16 when the assembly
comes out of the hole. Without the dual acting rupture disc 54 pressure
could have been trapped in space 16 and that could have been the cause
for injury to personnel that tried to separate mandrel 20 from extension
10. The dual acting rupture disc presents a compact solution to two
potential problems in an environment where space is at a premium. One or
more such rupture discs can be used and they are mounted in a port so
that in effect they take up no incremental space.

[0018] Those skilled in the art will appreciate that the debris barrier
and the bi-directional pressure equalization system can be applied to any
confined space between a subterranean tool and a running or a
running/setting tool. For the purposes of this application reference to
"running tool" will encompass tools that deliver other tools as well as
tools that also are configured to set another tool that was just
delivered. While the preferred embodiment for seals 30 and 32 is a
downhole oriented cup seal or a stack of such seals, other seal styles or
seal systems that can hold back debris while allowing pressure
equalization during run in are also contemplated. For example a bypass
system through the seal or around the seal that is actively open as the
assembly is run in and closed when the desired location is reached will
be a suitable alternative. Using the downhole oriented packer cups
however, eliminates the need for openings in the seals or in the mandrel
around the seals or shifting the seals to expose a bypass path. The
ability of the equalizing flow to simply displace the packer cups
temporarily and then snap back to the debris barrier position, makes the
design simpler, cheaper and more reliable. While the seals 30 and 32 are
depicted as mounted to the mandrel 20 mounting the seals to the sleeve 10
with the same downhole opening orientation is also contemplated.

[0019] The dual acting rupture disc is a space saving solution to
potential collapse of extension 10 and potential injury to surface
personnel that disassemble the mandrel 20 from the extension 10 if for
some reason they come out of the hole together with trapped hydrostatic
pressure between them. While the application has focused on a packer
running tool where setting dogs needed to be protected from fouling with
grit and debris in the drilling mud and the borehole, other applications
are envisioned such as anchors or fishing tools, for example. The use of
a solid rather than segmented ring 46 and its placement close to the top
14 of the sleeve 10 also acts to limit the number of solids that can
accumulate over seal 30 over time. Seal 32 acts a backup to seal 30
should there be any damage to seal 30.

[0020] The above description is illustrative of the preferred embodiment
and many modifications may be made by those skilled in the art without
departing from the invention whose scope is to be determined from the
literal and equivalent scope of the claims below: